I've only lived here for about a year and a half. Haven't really hooked up with anyone who can tell me much about where to do some mild trails. Have a basically stock '95 Wrangler, and just want to see some countryside that most people won't drive to.
Come a little south into Northern Colorado, and you can try several great trails.
Kelly Flats in the Poudre Canyon is a great moderate to "difficult in places trail."
There is Moody Hill and Crystal mountain up the Buckhorn Canyon just west of Ft Collins as well as Storm Mountain.
If you like a scenic drive there is the Cherokee Park road that goes between hwy 287 North of Ft Collins west to the Laramie River valley, it has a number of side roads that are a little challenging for wheeling and very scenic. Just stay on the designated roads and enjoy the scenery, worth the 20 minute drive from Cheyenne.
i'll have to make a note of those dunes and check them out sometime. vedauwoo and the surrounding area has some trails that i've been exploring occasionally in my free time and some of them are fun but some just seem like a dirt road...might have to check the snowies myself sometime since i havent been up that way for offroading
There's a few areas with roads less traveled in Blair Wallis, near Veadawoo (sp?) that are worth driving on. You could also make the trek to the Snowies outside of Centennial, there are countless lightly used roads in that area. I've been camping in the snowies my whole life and haven't explored every road.
Snowies are great, theres a lot (too many in my opinion) of trails there. Also, in the Laramie peak area there's a few. The one up Black Mtn for instance is definitely a Four wheel only trail and has quite a view at the top. Also a long winding trail at the top of Albany peak.
The Roads on the west side of the Snowies especially, which wind north off of the highway, are quite remote. There is a Road coming up French creek too that can test your nerve a bit over some boulder fields, with incredible wild flowers in the summer. REally, just get out and explore, their are quite a few trail in that area.